This invention relates to measuring rapidly varying air flow.
The need for such measurement arises in testing the accuracy of transducers in air flow, volume, and pressure measuring equipment, and in generating measured air flows, e.g., for respiratory application to a patient undergoing medical treatment. For the former application, it is desirable to be able to measure the transducer's response at high frequencies of air flow rate variation. For the latter application, it is desirable to measure accurately and conveniently the volume of gas delivered over a wide range of frequencies of air flow rate variation.
Emerson U.S. Pat. No. 2,918,917 describes the generation of high frequency air pulses with a diaphragm in a chamber. Pressure in the delivery tube to the patient is displayed on a gauge, and a pressure vent in that tube can be opened or closed with the thumb.
Venegas U.S. Pat. No. 4,155,356 shows various ways to generate a series of air pulses, including a movable diaphragm. Pulse control is by manually operated dials, cardiac measurements, and a pressure measurement made inside the patient.